Reply by Vrtigo1

You may have applied too much pressure. If you use too much it can force the wood to move out of alignment. There is bound to be some movement and it is unrealistic (at least in my experience) to expect things to come out of the clamps perfectly smooth, you will always have to do some post glue sanding. To aid alignment you could use biscuits when doing the final glue. The biscuits will help keep everything aligned. If you don’t have a biscuit jointer you could also just use some splines although you would see those on the ends of the board. If you used a contrasting wood it might not be bad though. 30 minutes w/ 60 grit paper does seem like an excessive amount of sanding, maybe someone else will weigh in with another solution.